1. Field of the Invention
This invention relates to apparatus for the measurement of the wall thickness of a coated rod and for ascertaining the eccentricity of the rod core with respect to the coating.
2. Description of the Prior Art
Electrical conductors are frequently coated with an insulating material. It is important to control the thickness of the coating as it forms a measure of the voltage capacity of the electrical conductor. For this reason, it is essential that the coating be formed concentrically around the conductor. Every eccentricity leads to a reduction of the dielectric strength of the jacket for the conductor.
The invention is obviously not limited to coated rods, but rather to any rod core used for the conduction of current or voltage.
It is known to ascertain the total diameter of a coated rod with a series of measuring apparatuses. These work either through contact or without contact. The former measuring method has a disadvantage when the diameter of the rod is measured immediately beyond the extrusion apparatus where the coating material is proportionately soft. For this reason contactless measuring methods, for example optical measuring methods, are of advantage. Fundamentally, with the use of this measuring process, however, it is not possible to determine or continuously indicate any eccentricity of the rod core with respect to the coating.